While it may seem like Linux-only projects are betraying their loyal base by developing Windows or OSX versions, I would argue that cross-platform development is actually better for Linux as a whole, better for individual software projects and their developers, and ultimately better for Linux users.

So I can run everything my Linux runs, but have games and proprietary application support too??? How does this help get me off of Windows again? The real answer is Linux needs better Linux only applications. Like Macintosh, the platform has to kick the crap out of Windows in specific areas to drive adoption. Right now it doesn't so it lags behind in marketshare.

Well TBH - you're irrelevant. I am, too. When talking about some respectable (not outright dominating, or some other silliness like that; first things first ;p ) market share, it matters only if the thing will be good enough for large enough group of people.

When I look at how the "average user" people around me use PCs - it turns out most of them aren't into Windows games at all (and out of those who aren't, the subgroup playing browser/etc. games seems bigger than "true PC gamers").
Also, while they technically do rely on "proprietary application support" - in large part (I think easily more than half...) it boils down to the browser, IM client, media player, and office suite (in many cases the last is already OOo/Libre Office, my place leads in their adoption as is - but TBH, when I sometimes see how people use Writer or Word (yes, that's also about large part of those who are convinced they "require" MS Office), something between Wordpad and Abiword would be more than enough for them)

They aren't really tied to the OS already (plus most don't use the OS per se, they just want from it to get out of their way) And while, in their cases, even habits could prevent that - there are still ~5 billion people who are not PC users - quite a space to grow among them. Coincidentally, they are the people who would appreciate lower costs the most (when underlying OS won't matter so much, something like not-in-your-way-LXDE might do fine - that's even one of their goals, to target inexpensive ARM-class hardware)